As a size of a Metal-Oxide-Silicon Field Effect Transistor (MOSFET) becomes smaller and smaller, especially when a feature size of the device enters a nanometer scale, a negative influence of a short-channel effect of the device also becomes more and more apparent. A Drain-Induced Barrier lowering (DIBL) effect and a band-to-band tunneling effect make an off-state leakage current of the device larger and larger, and as a threshold voltage of the device lowers, a power consumption of the integrated circuit increases. Moreover, due to theoretically limited by KT/q, a subthreshold slope of the conventional MOSFET device cannot decrease as the device size reduces simultaneously, and a subthreshold leakage current rises continually as the threshold voltage lowers. In order to overcome more and more challenges faced by a nanometer-scale MOSFET, novel device structures and preparation methods have become focus of small-size devices.
Early in 1960s, Lepselter and Sze put forwards a Schottky Barrier MOSFET structure. A conventional doping is replaced by a metal or a silicide in a source and a drain, and a turn-on is realized by using a direct tunneling of carriers in the source. The Schottky Barrier MOSFET greatly lowers a source and drain parasitic resistance of the device and realizes an ultra-shallow junction of the source and drain, and its simple process requires a small heat budget, which provides a possible solution for a use of a high-K and metal gate material. However, a large off-state leakage current and a small on-state current of the Schottky junction greatly limit an application the Schottky Barrier MOSFET device. Moreover, as to a problem of the theoretic limit of 60 mv/dec for the MOSFET subthreshold slope, in recent years, researchers have put forwards a possible solution, that is, by using a Tunneling Field Effect Transistor (TFET). The TFET uses the gate to control the band-to-band tunneling of a reversed-biased P-I-N junction so as to realize the turn-on, and the leakage current is very small. The TFET has many excellent features such as a low leakage current, a low subthreshold slope, a low working voltage and a low power consumption. However, as limited by a source junction tunneling probability and a tunneling area, the TFET faces a problem of a low on-state current, just like the Schottky Barrier MOSFET. Patent (CN101719517A) discloses a Schottky tunneling transistor, which solves a problem of a source/drain self-alignment of a TFET device by using a Schottky junction in the source and drain. However, the problem of small on-state current is still to be solved.